EFFECTS OF IRRIGATION AND NITROGEN-FERTILIZATION ON THE WATER RELATIONS OF PRUNUS-AVIUM AND COLT (PRUNUS-AVIUM L X P-PSEUDOCERASUS LIND)IN THE NURSERY, AND RESIDUAL EFFECTS AFTER OUTPLANTING

One year old Prunus avium seedlings and hardwood cuttings of 'Colt' were lined out in a nursery and given supplementary nitrogen fertilizer and/or irrigation. Irrigation increased leaf conductance (g(s)) and leaf water potential (Psi) in both genotypes but nitrogen did not affect these variables. In the following year, after outplanting, the residual effect of irrigation reduced g(s) compared with plants that had received no previous irrigation. Leaf conductance was greater and Psi was lower in Prunus avium as compared with 'Colt' each year. The greater g(s) for P. avium led to greater water use per unit leaf area in this genotype. However, on a whole-plant basis, water use was approximately equivalent for each genotype due to a larger total leaf area on 'Colt'. Water availability was the dominant factor in establishing early growth in these genotypes.